Rattling sound

[JakeOfAllTrades]

Just yesterday, a noise started coming from the return box closest to our 4 ton package unit....at least that's where we first noticed it.

Now you can hear the rattling all over the house and it sounds like the fan bogs down just a tad when the rattling takes place.

The noise started out sporadic, but has gotten progressively worse.

Any ideas what this could be before I tear the unit apart?

[HayZee518]

check for a loose tightening bolt on the motor frame. if its a belt drive, this bolt tightens the belt but if it's loose then the fan motor will bounce around. if it's a direct mounted squirrel cage fan, check to see if it is moving on the shaft and hitting the housing. if this is the case once you tighten the fan on the motor shaft use a second allen head set screw to lock the first one on the shaft.